Tool body for a shell end mill and cutting tool

ABSTRACT

A tool body ( 12 ) for a shell end mill ( 10 ) is described with at least one helical chip guiding groove ( 24 ) arranged at the circumference of the tool body ( 12 ) for chip dissipation and at least two receptacles ( 28 ) for indexable cutting inserts ( 26 ) arranged at the chip guiding groove ( 24 ). In this case, the receptacles ( 28 ) each comprise a base surface having a bore for receiving an indexable cutting insert fastening screw ( 34 ) and at least one first abutment surface adjacent to the base surface. The transition between the base surface and the first contact surface is a groove. In addition, a cutting tool is described with such a tool body, wherein a two-sided indexable cutting insert ( 26 ) is attached in each receptacle ( 28 ).

RELATED APPLICATIONS

The present application claims priority to U.S. patent application Ser.No. 15/238,214, filed on Aug. 16, 2016, the disclosure of which ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to a tool body for a shell end mill having atleast one spiral or helical chip discharge flute arranged on theperiphery of the tool body for discharging chips, and at least tworeceptacles, arranged on the chip discharge flute, for cutting inserts,wherein the receptacles respectively comprise a base surface with a holefor receiving a cutting insert mounting screw, and at least one firstcontact surface, which adjoins the base surface and is substantiallyorthogonal to the base surface.

The invention furthermore relates to a cutting tool, in particular ashell end mill, with a tool body of the type mentioned above.

BACKGROUND

Such tool bodies and cutting tools are known from the prior art. Shellend mills, which as a rule have a circular cylindrical basic shape, areused for machining tasks, in which a cutting process is to take placeboth on the end surface and on the shell surface of the shell end mill.For this purpose, the shell end mill comprises cutting edges, which areconstituted for example by cutting inserts, both on the end surface andon its shell surface.

As a rule, a shell end mill of the type mentioned above, or moreprecisely its tool body, comprises several chip discharge flutes. Oneach chip discharge flute, a multitude of cutting inserts mounted onreceptacles is arranged. Such a shell end mill thus comprises amultitude of cutting inserts and just as many associated receptacles.The designs of the respective tool body and of the cutting tool as awhole are therefore complex and accordingly expensive.

During the tool life, the price of a cutting tool is included in themachining costs. For this reason, machining a tool using a cutting toolof the type mentioned above, which comprises a tool body of the typementioned above, is expensive.

SUMMARY OF THE INVENTION

The task of the invention is therefore to further improve cutting toolsof the type mentioned above. In particular, the cost effectiveness ofsuch tools in the machining of tools is to be improved.

The task is solved by a tool body of the type mentioned above, in whichthe transition between the base surface and the first contact surface isa flute. The base surface and the first contact surface thus do not forma physical edge. Rather, the flute at the transition between the twosurfaces constitutes a recess, i.e. material has been removed incomparison to surfaces abutting against each other directly. Thecross-section of the flute may be any shape, for example rectangular,circular or oval. By means of the flute, double-sided cutting inserts,which are characterized by comprising cutting edges on both sides, canbe arranged in the receptacles. A quadrangular, double-sided cuttinginsert thus has eight cutting edges, a triangular cutting insert hassix. The flute is arranged such that a cutting edge, which lies on theside of the double-sided cutting insert that is not used for the cuttingat the time, can be received therein. The cutting edge is arranged onthe inside of the flute and does not contact the end faces of the fluteand thus not contact the tool body. A precise positioning of thedouble-sided cutting insert using the base surface and the first contactsurface is thus still possible. By using double-sided cutting insertsinstead of single-sided cutting inserts, the cost effectiveness of thecutting tool and the tool body in machining is increased.

In one embodiment, the tool body comprises between two and ten,preferably between five and seven chip guiding grooves. More chipguiding grooves are also possible. The number of chip guiding groovescan be determined considering the cutting task to perform and the sizeof the tool body.

In another embodiment, between three and thirty, preferably between fiveand twenty receptacles are arranged along each chip guiding groove ofthe tool body. It is also possible to have more receptacles depending onthe length of the tool body and the cutting task to be performed.

Preferably, the flute lies at least partially behind the base surfaceand behind the first contact surface. The flute is thus set back withrespect to the base surface, when viewed orthogonally to the basesurface. The flute is also set back, when viewed orthogonally to thefirst contact surface. There is thus enough space for receiving acutting edge of a double-sided cutting insert. The cutting edge alsodoes not come into contact with the delimiting walls of the flute or thetool body during the mounting and aligning of the cutting insert and istherefore protected.

In one embodiment, the base surfaces enclose different angles with alongitudinal axis of the tool body. This angle, which is called analignment angle or tool-sided machining angle, significantly affects thecutting result. In particular, all base surfaces that are provided onthe end surface of the tool body for receiving cutting inserts forcutting may have a different alignment angle than the other basesurfaces. Depending on the cutting task, the alignment angle may howeveralso be defined individually for each base surface. The individualalignment angles as are calculated in the course of an optimizationmethod, for which the finite element method can be used. Thus, the realentrance and exit angles of the indexable cutting inserts mounted on therespective recordings can be considered. In this way, a high qualitycutting result can be achieved in a cost-effective manner.

One design variant provides that the receptacle comprises a secondcontact surface that adjoins the first contact surface and the basesurface. A cutting insert mounted in the receptacle is thus secured onthe base surface using a cutting insert mounting screw and positioned byabutting against the two contact surfaces. The interaction of thecutting insert mounting screw and the respective mounting hole in thecutting insert can be designed such that the cutting insert is pulledagainst the two contact surfaces during tightening of the cutting insertmounting screw. In this case, one contact surface may be arranged suchthat it supports a cutting insert mounted in the receptaclesubstantially in an axial direction of the tool body and the othercontact surface is arranged to provide radial support. Thus, a preciseand simple positioning of cutting inserts is possible and cuttinginserts can be quickly exchanged and turned.

Advantageously, the transition between the first contact surface and thesecond contact surface is a flute. In the receptacle, cutting insertswith any corner radius can thus be arranged and abutted against thecontact surfaces. Like the flute at the transition of the base surfaceto the first contact surface, the flute at the transition between thetwo contact surfaces may also extend at least in regions behind each ofthese surfaces. Because any contaminations, e.g. in the form of chips,can be accommodated in the flute when the cutting inserts are abuttedagainst the contact surfaces, a precise positioning of the cuttinginserts is always possible.

In one design alternative, each receptacle is associated with a coolantoutlet opening arranged in the tool body for cooling a cutting insertreceived in the receptacle. In this way, higher cutting speeds and/ormaterial removal rates can be achieved with consistently high cuttingquality. Also with the cooling, the life span of indexable cuttinginsert, more specifically the cutting edge increases. The coolant outletopenings are designed such that they are directed toward a specifictarget region, e.g. toward the cutting edge, of a cutting insert mountedin the receptacle. Alternatively, each receptacle may also be associatedwith two or three coolant outlet openings.

Preferably, each coolant outlet opening communicates with a radialcoolant channel, whereby all radial coolant channels are connected to acentral coolant feed channel arranged axially in the tool body and theinterfaces between the radial coolant channels and the central coolantfeed channel are axially offset. At these interfaces, a coolant flow istransmitted from the central coolant feed channel to the respectiveradial coolant channels. The interfaces or connection points are spacedfrom one another in the axial direction of the tool body and thus alsoin the axial direction of the central coolant feed channel.Consequently, at each axial position of the central coolant feedchannel, there is only one interface or connection point. This allowsfor accurate and efficient cooling of the cutting process. At the sametime a tool body of high mechanical stability and strength is provided.

A variant provides that two coolant outlet openings are allocated tofirst two rows in each case as seen from the end face of the tool bodyfrom. The coolant outlet openings may be designed as twin openings, i.e.they are fed by a common coolant channel. The coolant may support thechip dissipation.

At least one coolant outlet opening for cooling a cutting process mayalso be arranged on the end surface of the tool body. These coolantoutlet openings also serve to increase the cutting speed and/or thematerial removal rate. A multitude of coolant outlet openings may alsobe arranged on the end surface.

Preferably, the tool body comprises between two and ten, preferablybetween five and seven, chip discharge flutes with receptacles forcutting inserts and the chip discharge flutes are in particulardistributed asymmetrically on the periphery of the tool body. In thisway, a tool body results, which ensures a cost-effective performance ofcutting tasks.

The tool body may be produced as one piece. In this case, a highmechanical stability of the tool body results. The tool body can bedesigned, for example, using the finite element method. In addition,such a tool body satisfies close tolerances, since mounting steps aredispensed with and no tolerance chain occurs. Precise and cost-effectivecutting is thus possible.

In a preferred embodiment, between three and thirty, preferably betweenfive and twenty, receptacles are arranged along the chip dischargeflute. On each chip discharge flute, the same number of cutting insertscan thus be mounted. In this way, cost-effective cutting is ensured.

An alternative embodiment provides that on the base surface a projectionfor centering of an indexable cutting insert is arranged, whereinpreferably the bore extends through the projection therethrough. Withthe help of the projection a indexable cutting insert mounted in thereceptacle may be oriented along the base surface, e.g., centered. Atthe same time, a positive connection between the projection and theassembled indexable cutting insert results parallel to the base. If thebore extends through the projection therethrough, the bore may bedesigned deeper in comparison with a receptacle without projection.Then, e.g., a long thread may be arranged in the bore. The installationof the indexable cutting insert is facilitated and the fastening of theindexable cutting insert is improved.

The task is also solved by a cutting tool, in particular a shell endmill, with a tool body according to the present invention, wherein adouble-sided cutting insert is mounted in each receptacle. Compared to acutting tool with single-sided cutting inserts, twice the number ofcutting edges is thus available. The tool life of the cutting tool isthus substantially doubled, which corresponds to a significant increasein cost effectiveness. The cutting inserts may have any shape, e.g.polyangular or round. The cutting inserts that are arranged on the endsurface of a chip discharge flute can be arranged for end-surfacemachining. The other cutting inserts are as a rule arranged forperipheral machining.

Advantageously, a cutting edge on the mounting side is arranged in theflute at the transition between the base surface and the first contactsurface.

The cutting inserts have a negative radial rake angle. The axial rakeangle can be positive or negative, depending on the cutting task.

In one variant, the cutting insert comprises two base surfaces on thecutting insert side, which are set back toward the inside of the cuttinginsert compared to the associated cutting edges. In other words, thecutting edges protrude the base surface in a direction orthogonal to thebase surface on the cutting insert side. A double-sided cutting insertcomprises two base surfaces on the cutting insert side, one on eachside. In the mounted condition, one of the base surfaces on the cuttinginsert side respectively abuts against the base surface on the tool bodyside. It is thus ensured that the cutting insert is precisely positionedin any position, i.e. in any rotary position or orientation.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be explained below with reference to variousexemplary embodiments that are shown in the accompanying drawings. Thefigures show:

FIG. 1 illustrates a cutting tool according to the present inventionwith a tool body according to the present invention in accordance with afirst embodiment with seven chip discharge flutes in a perspective view.

FIG. 2 illustrates a cutting tool according to the present inventionwith a tool body according to the present invention in accordance with asecond embodiment with five chip discharge flutes in a three-viewdrawing.

FIG. 3 illustrates a cutting tool according to the present inventionwith a tool body according to the present invention in accordance with athird embodiment with six chip discharge flutes in a three-view drawing.

FIG. 4 illustrates a detailed view of two cutting inserts of a cuttingtool according to the present invention, which are respectively mountedin a receptacle of a tool body according to the present invention.

FIG. 5 is a sectional view of an indexable cutting insert fastened in areceptacle of an inventive tool body.

FIG. 6 is an indexable cutting insert of an inventive cutting tool inplan view and sectional view.

FIG. 7 is a detailed view of an alternative embodiment of a receptaclefor an inventive tool body and

FIG. 8 is a schematic perspective view of the coolant channels of theinventive tool body, wherein the tool body is transparent.

DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by referenceto the previous and following detailed description and examples and theassociated figures. Elements and apparatus described herein, however,are not limited to the specific embodiments presented in the detaileddescription. It should be recognized that these embodiments are merelyillustrative of the principles of the present invention. Numerousmodifications and adaptations will be readily apparent to those of skillin the art without departing from the spirit and scope of the invention.

A shell end mill 10 comprises a tool body 12, which has substantially acircular cylindrical shape with a tool body longitudinal axis 14.

The tool body 12 comprises a clamping end 16 with which it can beclamped in a machine tool, not shown, and an opposite, machining end 18.On the machining end 18, an end face 20 is arranged.

The shell end mill 10 is designed for machining on its end face 20 andat its circumference 22. The circumference 22 may also be referred to asa lateral surface.

In the illustrated embodiment the tool body 12 is designedintegrally/monolithic.

In the tool body 12 chip guiding grooves 24 are arranged. These extendspirally or helically around the circumference 22 of the tool body 12and assist chip evacuation and/or the direction of chip flow.

In the illustrated embodiments, the tool body 12 comprises five, six orseven chip guiding grooves 24. Depending on the diameter of the toolbody and the size of the used indexable cutting inserts 26, the toolbody may also comprise more or fewer chip guiding grooves 24.

With particular reference to FIG. 2 and FIG. 3, the chip guiding grooves24 are unevenly distributed around the circumference 22 of the tool body12. This means that the angular spacings between adjacent chip guidinggrooves 24 are different in terms of distance.

At the chip guiding grooves 24 indexable cutting inserts 26 arearranged.

The indexable cutting inserts 26 are each set in a receptacle 28 anddesigned bilaterally. Such indexable cutting insert 26 is shown in FIG.6. However, there may be other, indexable cutting inserts, not shown inthe demonstrated shell end mill 10.

The receptacles 28 each comprise a base surface 30. A corresponding basesurface 32 of an indexable cutting insert 26 is located adjacent to thisbase surface 30. Then, the indexable cutting insert 26 is attached tothe receptacle 28 with an indexable cutting insert fixing screw 34,which engages in a hole 35 of the base surface 30.

Since these are two-sided indexable cutting inserts 26 in theillustrated embodiment, each indexable cutting insert 26 comprises twocutting insert base surfaces 32. As can be seen particularly in FIG. 6,the cutting insert base surfaces 32 are set back relative to cuttingedges 36, which are arranged on the same side.

The indexable cutting inserts 26 have a negative rake angle in theillustrated embodiment.

The inclination of the inserts 26 may be adjusted to the tool'slongitudinal axis 14 via the inclination of the base surface 30 to thetool body axis 14. The angle between the base surface 30 and thelongitudinal axis of the tool body 14 may be individually selecteddepending upon the cutting application for each base surface.

In the illustrated embodiment, the angles of each corresponding basesurfaces 30 are equal, which are arranged in adjacent chip guidinggrooves 24. This means, e.g., that all third base surfaces 30 andtherefore all third indexable cutting inserts 26 have the same anglealong the chip guiding grooves 24 with respect to the tool bodylongitudinal axis 14. However, the angle of the individual base areas 30differ within a chip guiding groove 24.

Further, the receptacle 28 includes a first abutment surface 37 and asecond abutment surface 38.

When assembled, the indexable cutting insert 26 is available with one ofits side surface 40 is located adjacent to the abutment surface 37 andthe abutment surface 38, respectively.

Both the first abutment surface 37 and the second abutment surface 38are adjacent to the base surface 30.

As seen in FIG. 5, the first abutment surface 37 is substantiallyperpendicular to the abutment surface 30. Similarly, the second abutmentsurface 38 is substantially perpendicular to the base surface 30.

Since rectangular or square indexable cutting inserts 26 are used in theillustrated embodiment, the first abutment surface 37 and secondabutment surface 38 are substantially perpendicular to each other.

The transition between the base surface 30 and the first abutmentsurface 37 is designed as a groove 42.

This groove 42 is designed so that it is located behind the base surface30, when viewed in a direction perpendicular to the base surface 30 andis located behind the first abutment surface 37, when viewed in adirection perpendicular to the abutment surface 37.

As seen in FIG. 4, the groove 42 may have a rectangular cross section.

In the receptacle 28 shown in FIG. 5, the groove 42 has a circular crosssection.

A comparable groove 30 of the base surface not shown is provided at thetransition to the second abutment surface 38.

As shown in FIG. 4, the transition between the first abutment surface 37and the second abutment surface 38 is also designed as a groove 44.

In the illustrated embodiment, the groove 44 has a circularcross-section, however, it may have any desired cross section as groove42.

If the indexable cutting inserts 26 are mounted in the seats 28, adifferentiation must be made between a clamping side of the indexablecutting insert 26 and a cutting side of the indexable cutting insert 26.The clamping side of the indexable cutting insert 26 is oriented towardsthe base surface 30. The cutting edges 36 on this side are not involvedin the machining. The cutting side is opposite to the clamping side. Oneof disposed cutting edges 36 on the machining side takes part in themachining.

In the assembled state of the indexable cutting insert 26, at least onecutting edge 36 is arranged in the groove 42 on the clamping-sided sideof the indexable cutting insert 26. This can be seen in FIG. 4 and FIG.5.

In an alternative embodiment of the receptacle 28, shown in FIG. 7, aprojection 48 is arranged on the base surface 30. On this projection 48the indexable cutting insert 26 may be centered during assembly. Forthis purpose, it must have a bore 35 associated with the geometry of theprojection 48. The centering projection 48 may be located, sized, and/orshaped to provide “easy” centering such that the indexable insert 26 maynot be seated without proper contact between the abutment surfaces 37,38, the indexable cutting insert 26, and the projection 48. Thus, alimited number of rotational, radial, lateral, and axial positions arepermitted with a projection 48 as illustrated in FIG. 7.

In the illustrated embodiment, the projection 48 has the shape of acircular cylinder and the bore 35 is arranged centrally in theprojection 48.

During assembly of the indexable cutting insert 26, it is firstprepositioned on the projection 48 and then arranged to the abutmentsurfaces 37, 38 in the course of screwing in the indexable cuttinginsert attachment screw 34.

In the illustrated embodiment, thirteen or seventeen indexable cuttinginserts 26 are positioned on each chip guiding groove 24. For clarity,only individual indexable cutting inserts 26 are provided with areference number. The number of indexable cutting inserts 26 at eachchip guiding groove may be determined, among other factors, depending onthe length of the tool body and the size of the indexable cuttinginserts 26 to be used.

The shell end mill 10 may be operated with the use of coolants orrefrigerants. Unspecified coolant channels are provided in the tool body12.

In the illustrated embodiment, each receptacle 28 and therefore eachindexable cutting insert 26 is associated with a coolant outlet opening50 being the end of a radial coolant channel 54, which is fed via by acentral coolant feed channel 56. Thus, the receptacle and indexablecutting insert received therein may be cooled during the machiningprocess. For clarity, only selected coolant outlet openings 50 areprovided with a reference mark.

Each two coolant outlet openings 50 may be associated to thosereceptacles 28, which are located in the first and second row viewedfrom the end face 20. Then, the coolant flow additionally supports thechip evacuation. This can be seen in FIG. 3. Likewise, the coolingchannels fed via coolant outlet openings 52 are arranged on the end face20 of the tool body 12.

In FIG. 8 the radial coolant channels 54 and the central coolant feedchannel 56 can be seen. The tool body 12 is not illustrated in thisfigure.

The radial coolant channels 54 connect the coolant outlet openings 50 tothe central coolant feed channel 56. The interfaces of the radialcoolant channels 54 and the central coolant feed channel 56 are spacedfrom each other, when seen in an axial direction, which corresponds tothe longitudinal axis 14 in the present embodiment. Therefore, the toolbody 12 has a maximum mechanical stability.

Various embodiments of the invention have been described in fulfillmentof the various objects of the invention. It should be recognized thatthese embodiments are merely illustrative of the principles of thepresent invention. Numerous modifications and adaptations thereof willbe readily apparent to those skilled in the art without departing fromthe spirit and scope of the invention.

The invention claimed is:
 1. A tool body for a shell end mill, the toolbody comprising: at least one helical chip-guiding groove arranged on acircumference of the tool body for chip dissipation; and at least threereceptacles arranged at the at least one chip-guiding groove, the atleast three receptacles including at least a first receptacle a secondreceptacle and a third receptacle, wherein the receptacles each comprisea base surface comprising a bore for receiving an indexable cuttinginsert fastening screw and at least one first abutment surface locatedadjacent to the base surface, the first abutment surface beingsubstantially perpendicular to the base surface, wherein a transitionbetween the base surface and the first abutment surface is a groove;wherein a two-sided, indexable insert is attached to each receptacle;wherein the base surface of the first receptacle for the at least onehelical chip-guiding groove has a first angle with respect to alongitudinal axis of the tool body; wherein the base surface of thesecond receptacle for the at least one helical chip-guiding groove has asecond, different angle with respect to the longitudinal axis of thetool body; and wherein the base surface of the third receptacle for theat least one helical chip guiding groove has a third angle with respectto the longitudinal axis of the tool body, and wherein the third angleis different from the first angle and the second angle.
 2. The tool bodyof claim 1, wherein each receptacle has a coolant outlet opening forcooling an indexable cutting insert in a respective one of thereceptacles arranged in the tool body.
 3. The tool body of claim 2,wherein the coolant outlet openings communicate with a plurality ofradial coolant channels, the radial coolant channels being incommunication with and extending radially outward from a central coolantfeed channel.
 4. The tool body of claim 3, wherein the radial coolantchannels are axially offset relative to one another such that, at eachaxial position of the central coolant feed channel, there is only oneinterface between the radial coolant channels and the central coolantfeed channel.
 5. The tool body of claim 1, wherein the tool bodycomprises at least two helical chip-guiding grooves arranged on thecircumference of the tool body for chip dissipation; and wherein thechip-guiding grooves are non-uniformly distributed along thecircumference of the tool body such that angular spacings betweenadjacent chip-guiding grooves are different.
 6. The tool body of claim1, wherein the tool body is integrally-formed as a monolithic body. 7.The tool body of claim 1, wherein a projection is arranged on each ofthe base surfaces, the projection being arranged for centering anindexable insert on each of the base surfaces; and wherein therespective bore of each of the base surfaces extends through theprojection arranged on each of the base surfaces.
 8. The tool body ofclaim 1 further comprising at least a second helical chip-guiding groovearranged on the circumference of the tool body, the second helicalchip-guiding groove comprising at least two receptacles arranged at thesecond helical chip-guiding groove, the at least two receptaclesincluding at least a first receptacle and a second receptacle, whereinthe base surface of the first receptacle for the second helicalchip-guiding groove has a first angle with respect to a longitudinalaxis of the tool body; and wherein the base surface of the secondreceptacle for the second helical chip-guiding groove has a second,different angle with respect to the longitudinal axis of the tool body.9. A cutting tool assembly comprising: a tool body comprising: at leastthree helical chip-guiding grooves arranged on a circumference of thetool body for chip dissipation; at least three receptacles arrangedalong each of the at least three helical chip-guiding grooves, the atleast three receptacles including at least a first receptacle a secondreceptacle and a third receptacle, the receptacles each comprising abase surface comprising a bore for receiving an indexable insert cuttingfastening screw and at least one first abutment surface located adjacentto the base surface, the first abutment surface being substantiallyperpendicular to the base surface; and a plurality of two-sidedindexable inserts, an individual one of the two-sided indexable insertsbeing attached to each of the receptacles, wherein the base surface ofeach of the first receptacles has a first angle with respect to alongitudinal axis of the tool body; wherein the base surface of each ofthe second receptacles has a second, different angle with respect to thelongitudinal axis of the tool body; and wherein the base surface of eachof the third receptacles has a third angle with respect to thelongitudinal axis of the tool body, and wherein the third angle isdifferent from the first angle and the second angle.
 10. The cuttingtool assembly of claim 9, wherein each receptacle has a coolant outletopening for cooling an indexable cutting insert in a respective one ofthe receptacles arranged in the tool body.
 11. The cutting tool assemblyof claim 10, wherein the coolant outlet openings communicate with aplurality of radial coolant channels, the radial coolant channels beingin communication with and extending radially outward from a centralcoolant feed channel.
 12. The cutting tool assembly of claim 11, whereinthe radial coolant channels are axially offset relative to one anothersuch that, at each axial position of the central coolant feed channel,there is only one interface between the radial coolant channels and thecentral coolant feed channel.
 13. The cutting tool assembly of claim 9,wherein the tool body comprises at least two helical chip-guidinggrooves arranged on the circumference of the tool body for chipdissipation; and wherein the chip-guiding grooves are non-uniformlydistributed along the circumference of the tool body such that angularspacings between adjacent chip-guiding grooves are different.
 14. Thecutting tool assembly of claim 9, wherein the tool body isintegrally-formed as a monolithic body.
 15. The cutting tool assembly ofclaim 9, wherein a projection is arranged on each of the base surfaces,the projection being arranged for centering an indexable insert on eachof the base surfaces; and wherein the respective bore of each of thebase surfaces extends through the projection arranged on each of thebase surfaces.
 16. The cutting tool assembly of claim 9, wherein thecutting tool assembly is a shell end mill.
 17. The cutting tool assemblyof claim 9, wherein the indexable cutting inserts have a negative radialrake angle.
 18. The cutting tool assembly of claim 9, wherein theindexable insert comprises two indexable side base surfaces locatedtoward an interior of the indexable cutting insert set back relative toassociated cutting edges.